#zhuti{
    height:100%;

}
#zhuti::before{
    background:  url('../img/logo1.png')  no-repeat fixed center;
    content:"";
    opacity:0.2;//透明度设置
    z-index:-1;
    width:2000px;
    height:1300px;
    position:absolute;
    /*top:0px;*/
    /*left:0px;*/
    /*border-radius:40px*/
}